1. Field of the Invention
This invention pertains to an apparatus more properly categorized as a system for generating a magnetic tape and then using the magnetic tape to control movement of a co-ordinate drive carriage carrying a tool over a workpiece to accomplish an operation on the workpiece, i.e. flame cutting of a specified shape. The system includes an apparatus for generating a tape containing signals, which signals correspond to the movement of a co-ordinate drive carriage as it moves in response to an optical line follower tracing the outline of a shape on a drawing. The tape is used to control movement of a co-ordinate drive machine used to produce the drawn shape in a workpiece and can produce a multiple number of shapes simultaneously by having a plurality of shape making devices (i.e. oxy-fuel cutting torches) mounted on the co-ordinate drive tool positioning apparatus.
2. Prior Art
Shape cutting machines used to cut patterned shapes from a workpiece are well known in the prior art.
Representative of early devices relying on a cam and cam follower to cause a machine to trace a specific pattern is disclosed in U.S. Pat. No. 2,546,116. Patentee discloses a device wherein the pattern is the cam and the cam follower is connected directly to an oxy-fuel torch. Patentee discloses use of magnetic devices in the drive train to cause movement of the torch to cut a pattern identical to that of a specified cam from a workpiece such as a steel plate.
Oxy-fuel or plasma contour cutting devices are disclosed in U.S. Pat. Nos. 3,423,081; 3,559,971; and 3,717,332. These three patents represent conventional oxy-fuel or plasma cutting devices utilizing a photo-electric cell which follows a pattern placed on a table. The photo-electric cell is connected to a drive mechanism which in turn is connected to a long arm on which are placed one or more oxy-fuel or plasma cutting torches. As the photo-electric cell traces the pattern, movement is transmitted by the direct coupling of the torches to the photo-electric cell so that the trace pattern is reproduced in a workpiece disposed beneath the torches. Such devices require the pattern to be exposed to all of the atmosphere of the shop employing oxy-fuel cutting.
Attempts at eliminating the need for an optical tracer and drawing in the shop area lead to the use of numerical tape control systems such as disclosed in U.S. Pat. No. 3,591,157 wherein patentees disclosed the use of a tape control to move the torches in a pattern dictated by the punched tape. Such tape control devices have also been applied to fabric cutting as disclosed in U.S. Pat. No. 3,991,706 and to cutting anisotropic sheet material with a small cutting wheel such as disclosed in U.S. Pat. No. 3,772,949.
A magnetic tape driven flame cutting machine is disclosed in U.S. Pat. No. 3,153,109. Patentees disclosed the need for photo-electric sensors which are coupled to the tape drive circuit to start and stop the tape drive. Patentees do not disclose how the tape is generated.
Another magnetic tape drive mechanism used in conjunction with a cloth cutting device is disclosed in U.S. Pat. No. 3,614,369.
Lastly, U.S. Pat. No. 3,368,803 discloses a line follower type flame cutting machine wherein a multiplier circuit is used so that small line drawings can be translated into large size shapes to be cut by a torch or torches suspended from a carriage which is carried between two spaced apart rails. This apparatus, like all of the prior art devices relying on an optical line follower connected directly to the torches or other cutting tools, has a serious drawback in that the pattern must of necessity be prepared for use in the field. This means that multiple patterns must be prepared if several machines are used to cut patterns. Likewise, each machine requires an optical line follower, thus increasing the complexity of the machine. Care must be taken to prevent dirt from settling on the drawing or other foreign objects being placed in the vicinity of the line on the drawing lest the optical tracer trace such aberations and thus produce defective pieces of product.
The optical line follower is desired as a drive means because of its unique ability to faithfully follow a line drawing resulting in a finished part with very high dimensional accuracy.